SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = '7b3d8e95fe0ed757ab1af137c8b8e552735ed3034856e9a4469021b86af4107f' 
  AND token = 'QVXjT+MDpqkm4kkRobT/HpKR54f6YGtokaWPRpT4IGc=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00034

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}